1. Field of the Invention
This invention relates generally to the suppression of interference amongst communication signals. In greater particularity, the invention relates to an interference canceler capable of canceling a wide variety of interferers using simple processing and simple hardware.
2. Description of Related Art
Radios may receive three forms of signals: noise, interference and communication. Noise can be caused naturally by lightning and the like and is largely unpredictable. Few steps are taken towards its elimination. Interference can be caused inadvertently, such as by the broadcasting of several stations on the same band, or can be caused deliberately, such as by the transmission of signals to intentionally mask communication signals. A number of techniques are used to combat interference.
Adaptive filtering is one technique used in military radios to cancel narrowband interference non-Gaussian in structure.
Two main categories of adaptive filters exist. One category is adaptive Wiener filters. In Wiener filters, weights are typically determined through the statistics of the temporal correlation of signal samples. A second category of adaptive filtering is adaptive locally optimum processing. Typically, such processing requires the calculation and use of the magnitudes and phases of complex samples and is commonly accomplished in serial steps involving weight calculations based upon the statistics of the samples taken. The weights are adapted to minimize the average magnitudes of the filter outputs.
Less complex and more efficient adaptive interference filters are needed to cancel both narrowband and broadband interferences.